Sampson,— The Morphology of 
III. General Morphology of the Tuber. 
The tuber of Phylloglossum has in turn been compared with the 
adventitious buds borne on the roots of Ophioglossum } the tuber of Orchis , 2 
the droppers of certain Monocotyledons,^ and the ‘protocorm’ of L. 
cernuum . 4 
The present paper seeks to bring forward anatomical data which throw 
new light upon the morphology of this plant. It is suggested that Phyllo- 
glossum is derived from some Lycopod possessing a branched vegetative 
system, which has become reduced and specialized in the adoption of 
a geophytic habit. The sharply defined pedicillate cone and the specialized 
storage tuber are advanced characters, and the juxtaposition of these with 
the frequent occurrence of feebly developed leaves and the absence of 
phloem from the stem is evidence that Phylloglossum is a reduced form. 
Examples of branching in Phylloglossum have hitherto been limited to 
a few isolated cases of dichotomy of the strobilus, but, as a result of 
an anatomical study, it is believed that branching occurs at least once in the 
yearly growth of every fertile plant, namely, on the formation of its annual 
tuber. 
The details in vascular anatomy, upon which this view is based, will be 
dealt with under the following heads : 
(a) Stelar anatomy of a large fertile plant. 
(b) Origin, form, and course of the tuber stele in fertile plants. 
(< c ) Leaves connected with the tuber stele. 
IV. Vascular Anatomy of Fertile Plants. 
(a) The Stelar Anatomy of a large Fertile Plant . 
Considered generally, the most striking features in the internal 
anatomy of Phylloglossum are the frequently medullated protostele, the 
mesarch position of the protoxylem, and the marked degradation of 
vascular tissue. The last point is illustrated by the almost complete 
absence of phloem, the breakdown of the protoxylem in the leaf-traces 
and in the stem, and the frequent occurrence of weakly formed tracheides. 
In Phylloglossum the plan of the stele depends largely on the size 
of the plant and the number and position of tubers, leaves, and roots, 
and it is therefore not easy to give a general description. If Phyllo- 
glossum be a form which has suffered reduction relatively recent in 
descent, the largest and best developed specimens would be those in 
which the more primitive features might be expected to occur. It is 
1 van Tieghem : Recherches sur la symetrie de structure des plantes vasculaires. 1871. 
2 Mettenius : loc. eit., 1867. 3 Wernham : loc. cit. , 1912. 
4 Treub : loc. cit., 1889-90. 
